image by Jörg Krüger (Image rights)
The Petri MF-3 is an SLR from 1978, at the point when Cosina had begun manufacturing Petri-branded cameras. This model is a adaptation of the Cosina CS-1, which means it accepts K mount lenses (unlike the MF-2 which used M42), and it is a rather well-specced manual exposure model. Interestingly, the MF-3 has a blank cap above the PC connector, in the place where the CS-1 has a socket for their rather Rube Goldberg AEC Adapter, a motorized shutter-dial rotator providing primitive autoexposure.
The MF-3 is based around an electronically-timed cloth shutter which ranges from 4 seconds to 1/1000, requiring two 1.5 volt silver-oxide batteries. These also power the TTL metering display, with ( + OK - ) LEDs at the top of the viewfinder image. Flash sync is at 1/60th second. The MF-3 has an electronic self timer with a front-facing countdown LED, and its baseplate can couple with a motorized winder. The rewind release is tucked alongside the advance lever, rather than on the bottom of the body.